1. Field of the Invention
The present invention relates generally to flat heat exchanger plates for use in heat exchangers. More particularly, relating to flat heat exchanger plates used in bulk material type heat exchangers.
2. Description of the Prior Art
Typically, in processing bulk materials, such as pellets, granules, powders or the like, heat exchangers are employed to either cool or heat the material during the processing thereof. The heat exchangers employed consist of an array of heat exchanger plates arranged side-by-side in spaced relationship and are positioned in an open top and open bottom housing. The like ends of each heat exchanger plate are connected to together by means of a manifold and a heat exchange medium, such as water, oil, glycol or the like is caused to flow through the plates. Generally, the material treated by the heat exchanger is allowed to gravity flow through the housing and the spaces between the spaced plates. During the progression of the material through the heat exchanger, the material is caused to contact the walls of the plates thereby effecting heat transfer between the material and the plates. The rate at which the material flows through the heat exchanger and ultimately across the plates can be controlled by restricting the flow of the material at the outlet of the heat exchanger.
The heat exchanger plates are constructed by attaching metal sheets together along the edges thereof and this is normally accomplished by seam welding the sheets together to form a fluid tight hollow plate. Heretofore, heat exchanger plates have been constructed to operate under internal pressure caused by pumping the heat exchange medium through the plate. To resist internal pressure and to prevent the sides of the plates from deforming, depressions or dimples are formed along the plate. An example of similar heat exchanger plates and their use are described in U.S. Pat. No. 6,328,099 to Hilt et al. and U.S. Pat. No. 6,460,614 to Hamert et al.
During the normal operation of the heat exchanger the bulk material tends to accumulate within the dimples or spot welds and continues to collect to a point where the efficiency of the heat exchanger is greatly reduced and must be cleaned to remove the material residue from the dimples and surrounding exterior surface of the plates. In some circumstances, the material is allowed to collect to a point where the material will bridge between adjacent plates; this not only reduces the heat transfer efficiency of the heat exchanger, but also restricts the flow of the material through the heat exchanger. These circumstances are very undesirable because the operation of heat exchanger must be shut down for a period of time to clean the plates, which many times means the material production line is also shut down, resulting in loss of production and ultimately loss in profits.
Therefore, a need exists for a new and improved flat heat exchanger plate that can be used for bulk material heat exchangers which reduces the tendency for the material to accumulate on the plates. In this regard, the present invention substantially fulfills this need. In this respect, the flat heat exchanger plate according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of increasing the efficiency of bulk material heat exchangers and reducing down time thereof.